1. Field of the Invention
The present invention relates, generally, to a method of manufacturing a printed circuit board (PCB), and more particularly, to a method of manufacturing a PCB using an imprinting process, which is advantageous because a pattern having a large area can be uniformly formed using a plurality of molds, and the plurality of molds is sequentially removed to solve problems occurring in release of the molds from an insulating layer.
2. Description of the Related Art
Recently, techniques for directly mounting semiconductor chips on PCBs, instead of CSP (Chip-Sized Package) mounting or wire bonding mounting, are increasingly required to correspond to high densities and high signal transfer speeds of semiconductor chips. In order to directly mount the semiconductor chip on the PCB, a highly dense and reliable PCB, corresponding to the high density of the semiconductor, must be developed.
Requirements for a highly dense and reliable PCB, which are closely concerned with specifications of semiconductor chips, include fineness of circuits, high electrical properties, high signal transfer speed structures, high reliability, multiple functionality, etc. Thus, such requirements are expected to be satisfied through techniques for manufacturing a PCB, capable of forming a fine circuit pattern and a micro-via hole.
Typically, a PCB has been manufactured using a photo-lithographic process that is advantageous thanks to its high productivity and low manufacturing cost. The photo-lithographic process for the formation of a fine circuit pattern on a PCB includes applying a photo-resist to a uniform thickness on a substrate, exposing and developing selected regions of photo-resist, forming a plating layer of conductive material, removing the residual photo-resist, and removing the unnecessary electroless plating layer of conductive material through etching.
However, the conventional method of manufacturing a PCB using such a photo-lithographic process entails two disadvantages as mentioned below, upon formation of an L/S of 10 μm/10 μm or less, in which “L” means lines, defining the width of the line, and “S” means spaces between the lines.
First, the conventional method of manufacturing a PCB using a photo-lithographic process yields limited adhesion at the interface between the photo-resist and the substrate when the L/S is formed to 10 μm/10 μm or less.
Second, the conventional method of manufacturing a PCB using a photo-lithographic process entails a problem of undercut of the circuit pattern upon removal of the unnecessary electroless plating layer of conductive material, resulting in a disconnected or delaminated fine circuit pattern.
With the goal of overcoming such problems, U.S. Pat. No. 4,912,844, and US Publication Nos. 2004/0046288 A1 and 2004/0118594 A1, and Japanese Patent Laid-open Publication Nos. 2001-230526, 2001-320150 and 2004-152934 disclose a method of manufacturing a PCB using an imprinting process.
However, in cases where an imprinting process is applied to form a circuit pattern on a large PCB having a size of about 405 mm×510 mm or more for mass production, the following three problems are caused.
First, the conventional method of manufacturing a PCB using an imprinting process suffers because a substrate (or epoxy resin) is imprinted with a large mold (or stamp), and thus, a uniform circuit pattern is difficult to form.
Second, the conventional method of manufacturing a PCB using an imprinting process suffers because an adhesion phenomenon between the mold (or stamp) and the substrate (or epoxy resin) may occur upon release of the large mold (or stamp) from the substrate (or epoxy resin), and thus, the pattern imprinted into the substrate (or epoxy resin) may be easily damaged and previously designed fine circuit patterns are difficult to form.
Third, the conventional method of manufacturing a PCB using an imprinting process suffers because a large mold (or stamp) is prepared, and thus, the design of such a mold (or stamp) is difficult to vary and a lot of time and expense is required to vary the design.